Process for preparation of leatherlike sheet material with excellent lastability

ABSTRACT

Leatherlike sheet material is prepared by impregnating a nonwoven fibrous mat or napped cloth with a solution of polymeric material, coagulating the solution by wet method to form a homogeneous fine sponge structure without sticking to the fibers and then contacting the impregnated mat or cloth with a heated surface at an elevated temperature above softening temperature of the polymeric material to soften the polymeric material and to form a thin polymer film on the surface of the impregnated mat or cloth.

UnitedStates atent 1 Feb. 29,1972

Nakajo et a1.

[54] PROCESS FOR PREPARATEON OF- LEATHERLIKE SHEET MATERIAL WITHEXCELLENT LASTABILITY Shogo Nakajo, Nishinomiya; Yoshitami e le Kuxa bbefle au Inventors:

Luraray Co., Ltd., Kurashiki, Japan Nov. 12, 1968 Assignee:

Filed:

Appl. N0.:

Foreign Application Priority Data Nov.21,l967 Japan ..42/7 4906 Jan.23,1968 Japan ..43/4133 U.S.Cl ..117/64, l17/135.5, 117/652, 210/506,264/41, 264/48 Int. Cl ..B44d l/44 Field of Search ..117/63, 64,1355,143; 264/41, 49; 210/506, 507, 508

Primary Examiner-William D. Martin Assistant Examiner-William R. TrenorAttorney-Stevens, Davis, Miller & Mosher [57] ABSTRACT Leatherlike sheetmaterial is prepared by impregnating a nonwoven fibrous mat or nappedcloth with a solution of polymeric material, coagulating the solution bywet method to form a homogeneous fine sponge structure without stickingto the fibers and then contacting the impregnated mat or cloth with aheated surface at an elevated temperature above softening temperature ofthe polymeric material to soften the polymeric material and to form athin polymer film on the surface of the impregnated mat or cloth.

15 Claims, No Drawings PROCESS FOR PREPARATION OF LEATHERLIKE SHEETMATERIAL WITH EXCELLENT LASTABKLITY The present invention relates to aprocess for preparing leatherlike sheet materials having a high surfacehardness and an excellent lastability.

it is well known that sheet materials comprising fibrous substrate suchas unwoven or woven cloths and surfacing layer of polymeric material canbe used as substitutes for leather.

However, these sheet materials consisted of two distinctlydistinguishable layers, namely the substrate and layerof polymericmaterial, so that they didn't give as a whole an integrated feeling, andthe polymeric layer was so thick that the surface hardness was small andits lastability was inferior.

The object of the present invention is to provide a method ofpreparation of leatherlike sheet materials which have a thin coveredpolymer layer, give a good integrated feeling between the polymer layerand substrate, have a large surface hardness and show an excellentlastabilityj The method of-the present invention comprises; impregnatingnonwoven fibrous mat or fully napped cloth with a solution of polymericmaterial, coagulating the solution by wet coagulation to form ahomogeneous fine sponge structure, and heating the impregnated mat orcloth by contacting with a heated surface at an elevated temperatureabove the softening temsurface of the impregnated mat or cloth.

One of the most remarkable characteristics of the present invention isto form a thin film of polymeric material over the surface by raising tothe surface the polymeric material impregnated in the substrate by heattreatment with a heating surface and simultaneously by binding fluffswhich are rendered to be laid down by heating on the surface of thesubstrate into the polymeric material, instead of the well-known methodin which the layer of polymeric material is formed over 'the surface bycoating or pasting. Consequently, the layer of polymeric material of thesheet material obtained by the present invention is very thin in thethickness, large in the surface hardness and excellent in itslastability and forms a small gap between the polymeric material andfiber because fiber is contained in the covering layer of the polymericmaterial, so that air and moisture permeability is excellent.

The important point in the present invention is to coagulate theimpregnated polymer solution to form a homogeneous fine sponge structurewithout being adhered on the fiber.

If the polymer solution is coagulated so as to be adhered on the fiberto an extreme extent, or if it forms a heterogeneous sponge structurecontaining many big air bubbles, it becomes difficult to produce a flatthin film covering the whole surface of the impregnated mat or cloth,even by treatment with a heated plate.

One method, by which a homogeneous fine sponge structure can be formedfrom the impregnated polymer solution without being adhered on thefiber, is to keep the coagulating bath at a comparatively lowtemperature (preferably below 40 C.) and to decrease the solvent contentin the bath (preferably below 40 percent). Another method is preferablyto dissolve or disperse a nonsolvent for the polymer compounds, or asolid insoluble in the coagulating liquid into the impregnating polymersolution, this method can be most preferably used together with theabove-mentioned methods.

it is preferred that before the impregnated mat is heated, theimpregnated mat is covered with a material which can be converted into aliquid film having some affinity to the heated surface between theimpregnated mat and the heated surface when the mat was heated with theheated surface. We call this material an interposition substancehereinafter.

Even though the surface of impregnated mat is apparently even, it isvery uneven and rugged microscopically. Then heat transfer and press arenot uniform on such a surface when the surface is heated and pressed bya heating surface. These factors cause the difficulty to make the evencovered film on the surface. However, in the case when the impregnatedmat is covered with an interposition substance, the liquid film havingsome affinity to the heated surface is formed between the mat and theheating surface by treatment of the heating surface. Therefore the heattransfer and press to mat are efiected uniformly due to this liquidfilm. In this process, impregnated polymer in the mat is spread up andis converted into the thin and even layer on the surface.

The interposition substances include, for example, sorbitolmonostearate, various silicon resins, fatty acids, ethyleneimine,amides, various surfactants having carbonyl group.

Various surface can be used for heating the impregnated mat. Because itcan be used continuously, rollers heated by electricity, steam andheated fluids are most appropriate.

The temperature of the heated surface should be above the softeningtemperature of the impregnated polymer. lf polyurethane elastomers areused as polymeric material, the temperature should be above 180 C. andis most preferably 190 C. 240 C.

As a polymeric material, thermoplastic polymers can be used.Polyurethane elastomer is the best, and polyvinyl chloride, polyamideand polyacrylates can also be used. These may be used alone or inadmixture with other polymer.

The above explanation is for the unwoven fiber mats. The presentinvention can be applied to felts and other fully napped cloths.

The present invention is further set forth in the following ex amples.All parts and percentages are based on weight.

EXAMPLE 1 Needle-punched web was produced by using mixed-spun fibers (3denier, 50 mm.) of nylon 6 and polystyrene (50:50). The web wasimpregnated with a solution consisting of 20 parts of polyurethane, 7parts of dimethyl formamide and 3 parts of water in the amount of 400percent of weight of the web. The web was immersed in a coagulatingliquid consisting of 30 parts of dimethyl forrnamide and 70 parts ofwater at 30 C. for 20 minutes to coagulate polyurethane elastomer, andwashed with water. Then polystyrene in the fibers was extracted with hottoluene at C. Finally the web was dried by hot air at 120 C.

The impregnated mat was brought into contact with chromium-plated rollerhaving a surface temperature of 200 C. and polyurethane elastomerexisting in upper part of the impregnated web was softened and a thinfilm was produced over the surface.

The sheet material thus obtained had a thin surface-cover- Note (I): Thesurface hardness is the width of the scratch by Clemens method. (Weight200 g., Stainless pinhead, angle Note (2): The bending resistance is theload by Gahle method.

EXAMPLE 2 An woven cloth of a 1.0 mm. thickness, one sided which wasnapped, was impregnated with polyurethane elastomer, in the same manneras described in Example 1.

The napped side of the impregnated napped cloth was ironed by achromium-plated-plate at 240 C. As a result, the

polyurethane elastomer existing near thesurface of the cloth wassoftened and a surface film mixed with napped fiber's was formed.

As shown in Table 2, the sheet obtained had a thin surface film and alarge surface hardness and was a soft material.

TABLE 2 Thickness of the surface film (mm.) 0.03 Hardness of the surfacefilm (mm.) 0.05 Bending resistance (mg.) L000 the surface and form athin film of said polymeric material over the surface of the impregnatedmat or cloth.

2. A process as claimed in claim 1, in which coagulation is carried outat a temperature below 40 C.

3. A process as claimed in claim 1, in which the coagulation bathcontains less than 40 percent of solvent for the polymeric material.

4. A process as claimed in claim 1, in which the coagulation is carriedout in a coagulation bath which has a temperature below C. and containsless than 40 percent of solvent for the polymeric material.

5. A process as claimed in claim 1, in which the polymer solutioncontains a nonsolvent for the polymer.

6. A process as claimed in claim 1, in which the polymer solutioncontains a solid insoluble in the coagulating bath.

7. A process as claimed in claim 1, in which the polymeric material is apolyurethane elastomer.

8. A process as claimed in claim 1, in which an interposition substanceis applied to the impregnated mat or cloth before heating.

9. A process as claimed in claim 8, in which said interpositionsubstance is selected from the group consisting of sorbitolmonostearate,.a silicon resin, a fatty acid, ethylene-imine, an amide ora surfactant containing a carbonyl group.

10. A process for the preparation of a leatherlike sheet material whichcomprises impregnating a nonwoven fibrous mat or fully napped cloth witha solution of polyurethane elastomer, coagulating the solution bytreating the solution with a coagulating bath which has a temperaturebelow 40 C. and contains less than 40 percent of solvent for thepolyurethane elastomer to form a homogeneous fine sponge structurewithout adhering to the fibers, drying the impregnated mat or cloth, andthen heating the impregnated mat or cloth by contacting it with a heatedsurface at a temperature above C. for a sufficient time to soften thepolyurethane elastomer and cause said polymer to rise to the surface andform a thin film of said polymeric material over the surface of theimpregnated mat or cloth.

11. A process as claimed in claim 10, in which an interpositionsubstance is applied to the impregnated mat or cloth before heating.

12. A process as claimed in claim 10, in which said interpositionsubstance is selected from the group consisting of sorbitolmonostearate, a silicon resin, a fatty acid, ethyleneimine, an amide ora surfactant containing a carbonyl group.

13. A process as claimed in claim 10, in which the temperature of theheated surface is from to 240 C.

14. A process as claimed in claim 10, in which the solvent'forltshelgolyurethane elastomer is dimethyl formarnide.

29x3? UNITED s'rmflas PATENT OFFICE @ERTI'JFICATE OF CORRECTION patent3,645,776 'Dated February 29 197,2

lnveritoz-(s) Shogo Nakajo and Yoshi'tami Saito It is certified thaterror appears in the above-ideniffed patent and that said Letters Patentare hereby corrected as shown. below:

On the fir t page pl ea se e orrec't th e nQme 045 \the as signee' fromSigns d and sealed this 3rd deiy of Octobe'f- 1972 (SEAL) Attest:

EDWARD I IQFLETCHBRJH. I 4 h ROBERT GOTTSC'HALK Attestlng OfficerCommissionerof Patents

2. A process as claimed in claim 1, in which coagulation is carried outat a temperature below 40* C.
 3. A process as claimed in claim 1, inwhich the coagulation bath contains less than 40 percent of solvent forthe polymeric material.
 4. A process as claimed in claim 1, in which thecoagulation is carried out in a coagulation bath which has a temperaturebelow 40* C. and contains less than 40 percent of solvent for thepolymeric material.
 5. A process as claimed in claim 1, in which thepolymer solution contains a nonsolvent for the polymer.
 6. A process asclaimed in claim 1, in which the polymer solution contains a solidinsoluble in the coagulating bath.
 7. A process as claimed in claim 1,in which the polymeric material is a polyurethane elastomer.
 8. Aprocess as claimed in claim 1, in which an interposition substance isapplied to the impregnated mat or cloth before heating.
 9. A process asclaimed in claim 8, in which said interposition substance is selectedfrom the group consisting of sorbitol monostearate, a silicon resin, afatty acid, ethylene-imine, an amide or a surfactant containing acarbonyl group.
 10. A process for the preparation of a leatherlike sheetmaterial which comprises impregnating a nonwoven fibrous mat or fullynapped cloth with a solution of polyurethane elastomer, coagulating thesolution by treating the solution with a coagulating bath which has atemperature below 40* C. and contains less than 40 percent of solventfor the polyurethane elastomer to form a homogeneous fine spongestructure without adhering to the fibers, drying the impregnated mat orcloth, and then heating the impregnated mat or cloth by contacting itwith a heated surface at a temperature above 180* C. for a sufficienttime to soften the polyurethane elastomer and cause said polymer to riseto the surface and form a thin film of said polymeric material over thesurface of the impregnated mat or cloth.
 11. A process as claimed inclaim 10, in which an interposition substance is applied to theimpregnated mat or cloth before heating.
 12. A process as claimed inclaim 10, in which said interposition substance is selected from thegroup consisting of sorbitol monostearate, a silicon resin, a fattyacid, ethylene-imine, an amide or a surfactant containing a carbonylgroup.
 13. A process as claimed in claim 10, in which the temperature ofthe heated surface is from 190* to 240* C.
 14. A process as claimed inclaim 10, in which the solvent for the polyurethane elastomer isdimethyl formamide.
 15. A process as claimed in claim 10, in which thenonsolvent for the polyurethane elastomer is water.